1. Field of the Invention
This invention relates to electrical meters, and in particular to solenoid type voltage, polarity and continuity meters or testers.
2. Discussion of the Prior Art
Solenoid type voltage polarity and continuity testers are well known. They are preferred in many applications by electricians because they are capable of measuring a large range of voltages, either AC or DC, and because the solenoid movement of such meters is rugged. One such meter is disclosed in U.S. Pat. No. 4,503,390. In the circuit of this meter, the solenoid and a threshold voltage device in series with the solenoid are in parallel with the circuit which performs the polarity and continuity indicating functions. Two batteries are provided with a ground between the batteries and the same light emitting diode is used to indicate both a positive DC polarity and also continuity.
In this circuit, there is no practical way to test the continuity of the solenoid itself. Also, this circuit design requires two batteries with a ground between them and does not distinguish between a positive DC voltage and polarity continuity without switching the probes around and retesting.